<!DOCTYPE HTML>
<html>
<body>
  <div style="width:400px; height:500px; overflow:hidden; border:2px solid black">
    <div style="height:450px"></div>
    <div style="height:100px; width:200px; float:left; background:purple"></div>
    <div style="opacity:0.5">
      <div style="left:200px; top:0; height:800px; width:300px; float:left; background:yellow; position:absolute; z-index:1;"></div>
      <div style="height:100px; width:200px; float:left; background:purple; position:relative; z-index:2;"></div>
    </div>
  </div>

